[Studies on the serum types and identification efficiency on Diarrheagenic Escherichia coli isolated from diarrhea patients, in Zhejiang province].

Objective: To investigate the serotypes of Diarrheagenic Escherichia coli (DEC) isolated from diarrheal patients in Zhejiang province and to explore the identification efficiency of serological screening methods. Methods: Serological agglutination tests were carried out in 696 strains of DEC (through the identification of virulence genes) which were selected from the Infectious Diarrhea Pathogen Monitoring Network Strain Bank of Zhejiang province, from July 2009 to June 2013. Results of virulence genes, serological identification and classification were compared. Results: Among the 696 isolates of DEC, O antigen type was identified in 288 (41.4%) isolates which belonging to 35 different 'O' serum types. H antigen was seen in 171 (24.6%) isolates and determined as having 21 types. The agglutination rates of EAEC, ETEC, EPEC and EHEC isolates were 31.9% (130/408), 70.6% (127/180), 31.5% (29/92) and 14.3% (2/14), respectively and belonged to 30, 18, 15 kinds of 'O' sero-groups, respectively. One EHEC isolate was identified as O157∶H7. Serum groups were diverse for EAEC and EPEC, while relatively concentrated on ETEC. Different types of DEC might belong to the same sero-group or type. Among the 74 strains of DEC available for classification serologically, 41 isolates were in consistent with virulence gene identification and another 33 strains were not. Conclusions: The sero-group/type of DEC strains in Zhejiang were varied. Based on the serological screening method alone, DEC classification might end in getting the wrong answer, thus we would recommend the use of virulence gene for the purpose of identification.